FIELD OF THE INVENTION
The present invention relates to an integrally forged rigid support device
disposable between the tube elements sustaining harsh operating conditions
prevailing inside the fluidized bed combustion boilers.
BACKGROUND OF INVENTION
Heat transfer surfaces for example Superheater, Reheater and Evaporator
bundles are kept immersed inside inert bed material to recover the heat of the
solid particles available in the bed of fluidized bed combustion boilers. The tube
bundles are kept inside the bundle chamber and their inlet and outlet headers
are kept outside of the chamber and connected through other bundle of tubes
penetrating the walls of the bundle chamber. The tube bundles are either
suspended from top or supported from a bottom of the chamber based on
designed penetration locations of the tubes provided on walls of the bundle
chamber. There are a plurality of tube rows or parallel flow paths with defined
spacing in between the tube elements. In specific cases, the distance between
the tube elements of each column is very less which requires different type of
support. Just below the tube bundle, air nozzles are provided in a grate for
effective fluidisation of the bed material.
Normally the supports adopted for the horizontal heat transfer surfaces provided
in second pass of the conventional boilers face only flue gas flow as external
medium. But, in case of fluidized bed, the tube bundles are in physical contact
with the agitating solid particles since they are immersed in the fluidized bed.
Hence, conventional supports may not be adequate for fluidized bed
environment due to the dynamics of fluidisation. In some cases, the distance

between the tube elements of each column is very less which requires different
type of support. These tube bundles need to be supported inside the bundle
chamber considering the self-weight of the bundle, tube thermal expansion and
the dynamic forces due to fluidisation. The supports shall be sufficiently rigid
enough to take care of the above forces. Considering the operating regime inside
the fluidized bundle chamber, new support has been developed to support the
tube bundles inside the fluidized bed with less spacing between the tube
elements. The support envisages steam cooled forged hanger block with recess
provided along it to support the individual tube elements of the bundle. Half
sleeves are used to avoid slipping of the individual elements from the hanger
block.
It is known from US4307777 to support horizontal tubes of a heat exchanger
located in a flow of hot gas. The fluid cooled hanger tube includes two
longitudinally extending fins located on opposite sides of the hanger tube. The
fin is continuous throughout the height of the tube bank to be supported. A 'U'
strap is arranged to surround and support each of the horizontal tubes with both
the lower & upper leg of each 'u' strap being welded to the longitudinally
extending fins.
Furthermore, US4421070 discloses a steam cooled hanger tube for horizontal
Superheaters and Reheaters. A plurality of 'L' shaped lugs are welded on
opposite sides of the vertical hanger tube run. The horizontal tube portions are
located adjacent the vertical leg of the lug. A band surrounds each of the
horizontal tube portions and is welded to the lugs both above and below the
tube.
US4270599 presented a tube support structure for a Fluidized Bed Heat
Exchanger. A plurality of heat exchange tubes extend within the housing and are

supported by a support pier so that the air passing through the pier also passes
over the tubes. A ladder type support structure is provided between adjacent
tube sections to support the sections relative to each other.
US4619315 and US4637455 provided plate type support arrangement for
serpentine coils arranged in fluidized bed. These are in particular to apparatus
for supporting a tubular heat exchanger immersed in a fluidized bed.
The operating regime in the fluidized bed requires a rigid and reliable support for
continuous trouble free operation. To meet these operational requirement steam
cooled forged hanger has been envisaged as a support system for the tube
bundles.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an integrally forged rigid
support device disposable between the tube elements sustaining harsh operating
conditions prevailing inside the fluidized bed combustion boilers.
Another object of the invention is to propose an integrally forged rigid support
device disposable between the tube elements sustaining harsh operating
conditions prevailing inside the fluidized bed combustion boilers, which is
enabled to withstand thermal expansion forces and the dynamic forces of
fluidisation.
SUMMARY OF THE INVENTION
In fluidized bed combustion boilers, heat transfer surfaces like tube bundles are
immersed in the fluidized bed material which consists of inert particles and
crushed coal particles. The tube elements are subjected to internal steam

pressure, temperature and other dynamic forces of fluidization. The plurality of
tubes are arranged as rows and columns with predetermined spacing in between
the tubes. Sometimes, the distance between the tube elements of each column
is too close that requires a different type of support.
Thus, the invention provides a device for supporting the tube bundles in a
fluidized combustion boiler having small spacing between the tube elements
which are immersed in the fluidized bed. The operating regime in the fluidized
bed is different from the conventional boilers and require a rigid and reliable
support for continuous trouble free operation. A plurality of rigid steam cooled
forged hanger blocks have been envisaged as a support device for the tube
bundles with less spacing between the tube elements. The device ensures cooled
supports and enhances the reliability of the support device compared to
conventional plate supports particularly when operating in a fluidized bed
environment. The configuration of the support device allows easy manufacturing,
with less number of loose components and assembly is much easier in-situ
position.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows an overview of tube bundles for fluidized bed combustion
boilers
Figure 2 - shows elevation and plan view of the support device of the
invention
Figure 3 - shows an assembled view of the tube coils on the support device of
the invention

Figure 4 - shows an exploded view of the support device including the tube
coil in disassembled condition.
DETAILED DESCRIPTION OF THE INVENTION
The accompanying drawings may be referred for better understanding of the
invention.
As shown in figure 2, a vertical steam cooled forged hanger block (1) is
interposed between two horizontal coil (2) assemblies. A recess provided on the
forged hanger block (1) corresponding to the coil assemblies (2) to
accommodate the horizontal coils (2) on both sides. Upon insertion of the forged
hanger block (1) between the two horizontal coil (2) assemblies, the coil
elements are pushed into a semi-circular profile configured on both sides of the
forged block. One each half sleeve (3) is assembled from both ends of the
hanger block (1) to keep the horizontal coil elements (2) in position. The half
sleeves (3) are welded with the block (1) after inserting the coils (2) into the
position. The horizontal tube elements (2) maintained free from welding so that
the tubes can freely move along its length inside the block (1) due to thermal
expansion. Similarly, each pair of the remaining horizontal coils (2) is assembled
to the vertical forged hanger block (1). The number of forged hanger blocks (1)
per row of support is half the number of horizontal coil assemblies (2) since
there is one hanger block for each pair of coil assemblies. A deep hole provided
(not shown) on the forged hanger block (1) for full length to carry the steam and
thereby cool the forged hanger block (1). The forged hanger block (1) is welded
to a vertical hanger tube suspended from the roof casing of the bundle chamber
(not shown). There are two rows of support for the tube bundle to make it a
simply supported configuration.

WE CLAIM
1. An integrally forged rigid support device disposable between the tube
elements sustaining harsh operating conditions prevailing inside the
fluidized bed combustion boilers, comprising:
- a vertical forged hanger block (1) weldably connected to a vertical
hanger tube suspended from the roof casing of a bundle chamber
of the fluidized bed combustion boiler, the hanger block (1) having
a deep through-hole for receiving steam to cool the hanger block
(1), a plurality of semicircular recesses configured vertically along
the opposite sides of the vertical block (1) to detachably attach one
horizontal coil (2) on each recess;
- one each half-sleeve (3) located on both sides of the hanger block
(1) to hold the horizontal coils (2) in position and the sleeves (3)
welded with the block (1) such that the horizontal coils (2) remain
free from welding to allow free-movement of the coils (2) inside the
block (1) due to thermal expansion during operation of the boiler,
wherein the number of forged hanger block (1) per row of support is
half the number of horizontal coil assemblies (2).
2. The device as claimed in claim 1, wherein a plurality of horizontal coils (2)
including corresponding number of half-sleeves (3) are inserted on both
sides of the hanger block (1) along the vertical direction.

ABSTRACT

The invention relates to an integrally forged rigid support device disposable
between the tube elements sustaining harsh operating conditions prevailing
inside the fluidized bed combustion boilers, comprising a vertical forged hanger
block (1) weldably connected to a vertical hanger tube suspended from the roof
casing of a bundle chamber of the fluidized bed combustion boiler, the hanger
block (1) having a deep through-hole for receiving steam to cool the hanger
block (1), a plurality of semicircular recesses configured vertically along the
opposite sides of the vertical block (1) to detachably attach one horizontal coil
(2) on each recess; one each half-sleeve (3) located on both sides of the hanger
block (1) to hold the horizontal coils (2) in position and the sleeves (3) welded
with the block (1) such that the horizontal coils (2) remain free from welding to
allow free-movement of the coils (2) inside the block (1) due to thermal
expansion during operation of the boiler, wherein the number of forged hanger
block (1) per row of support is half the number of horizontal coil assemblies (2).